JQueryUI datetime picker is best option as it allows pro users to enter their own value in textbox or they can choose it from picker.
Setting up picker to allow easy entering of birthdays or future dates is pretty easy too:
$(‘#datepicker’).datepicker({
changeMonth: true,
changeYear: true,
yearRange: ‘-100:+50'
});
this shows something like this (cant post a photo as I'm new user: http://klalex.com/wp-content/uploads/2009/07/picture-1.png)
and yearRange shows dates from DateTime.Now.Year - 100 to DateTime.Now.Year + 50
found this on: http://klalex.com/2009/07/jquery-ui-datepicker-for-birth-date-input/